Verified answer

If she is giving you her plan then to get the iPhone u just need the data plan which is $15 or $25 depending on ur usage, and add a texting plan if needed.

If she is adding you to her plan then u would have to get a family plan for two phones with shared minutes and also add the data plan for $15 or $25, plus texting if needed.

I have AT&T and their customer service department is really great. If your grandmother wants to put you on her plan she can get a second line under her name. When i got my iPhone a year ago the representative i spoke to was really nice and she set me up with a great plan. if you call them they'll be able to tell you exactly which type of plan you should get and what would be the best one to get. Hope it helps and good luck with your iPhone; you'll love it.

unless your not 18 then don't read this. but really, i would just get on your own plan. i have an iPhone 4 on at&t on my own plan and pay around 87 a month. its sooo much better than being stuck on someone else's plan.